Automatic Measuring Instrument for Radon Daughters Concentration of Precipitation

摘要

An automatic measuring instrument for the radon daughters concentration of precipitation has been constructed and used successfully. The precipitation collected by a polyethylene funnel during 15 min is led to a glass cell set in a well-type NaI (T1) scintillator, and after 5 min counting the water sample is pumped out. A sequence of operations of sampling, measurement, recording, draining out and correction for the volume of the water sample is performed automatically, and is repeated at every 15 min. The instrument has sensitivity and durability enough for practical use at outdoors. This instrument enables the measurement of radon daughters concentration as low as 0.5 Bq/ml at precipitation rate as small as 0.5 mm/h.For the improvement of accuracy of the monitoring system of environmental γ-radiation, the effect of radon daughters accumulated on the ground surface by precipitation can be eliminated on real time by means of providing it with the output of this instrument.This instrument can be used for the measurement not only of the radon daughters but also of the other radioactive nuclides in precipitation.